Therapeutic agents, and in particular drugs, are commonly delivered to a patient, via a pill, capsule, tablet or the like that is ingested orally and absorbed into the bloodstream. A therapeutic agent may also be introduced directly into the bloodstream via an intravenous solution. Therapeutic agents that are ingested orally and absorbed require a longer period of time before the effects of the agent are realized by the patient. Furthermore, agents delivered to a patient via a pill, capsule, tablet or the like suffer from a loss of therapeutic effect due to hepatic metabolism. Intravenous drug delivery, however, is generally inconvenient for a patient that is not resident in a health care facility and can be painful under certain circumstances. Delivery of a therapeutic agent in the form of an aerosol by inhalation overcomes the disadvantages of both delivery methods, but has yet to gain widespread acceptance and use. One possible reason for the limited role of inhalation drug delivery despite its increased efficacy, convenience and painless administration is the lack of a suitable device for portable, reliable, repeatable and simplistic vaporization and delivery of a variety of different drugs in an aerosol form. Existing devices for vaporizing and delivering a therapeutic agent in the form of an aerosol are suitable for use with only a limited class of therapeutic drugs, such as drugs for the treatment of asthma. In addition, none of the existing aerosol agent delivery devices are sufficiently portable, reliable, repeatable and easy to use.
The adverse health risks associated with smoking cigarettes have been recognized for decades. Accordingly, approximately seventy percent (70%) of smokers today desire to reduce the amount of cigarettes they smoke, or want to quit altogether. Despite the known risks, only an estimated six percent (6%) of smokers are able to quit smoking entirely. The low rate of success is believed to be due to the highly addictive nature of nicotine present in conventional cigarettes. Nicotine gum and nicotine patches for the delivery of nicotine without the harmful by products of combustion have been available for years. Nicotine gum and nicotine patches, however, have proven to be largely unsuccessful smoking cessation devices due to their failure to satisfy the smoker's hand-to-mouth and inhalation urges. In the past few years, nicotine delivery devices in the form of combustion-free electronic cigarettes, commonly referred to as “smokeless cigarettes,” “e-cigarettes” or “e-cigs,” have been developed and introduced to the consuming public.
Popular brands of e-cigarettes include BLU ECIGS® offered by Lorillard Technologies, Inc. of Greensboro, N.C., VUSE® offered by Reynolds Innovations, Inc. of Winston-Salem, N.C., MARK 1O™ offered by Phillip Morris, Inc. of Richmond, Va., and NJOY® offered by NJOY, Inc. of Scottsdale, Ariz. Each of the aforementioned commercially available e-cigarettes replicate the hand-to-mouth and inhalation experiences of a combustion cigarette desired by smokers. At the same time, they satisfy a smoker's craving for the addictive nicotine without exposing the smoker to the carcinogenic by-products (e.g. tar) produced by the combustion of tobacco, as well as by-standers to second-hand smoke. As a result, e-cigarettes are credited with providing a healthier nicotine delivery option to smokers and a healthy environment to by-standers subjected to second-hand smoke by significantly reducing, and potentially eliminating, the harmful effects of the carcinogens present in the smoke that would otherwise be produced and dispersed by lighting and smoking a traditional combustion cigarette.
Traditional combustion cigarettes are made of a combustible material that is ignited with a flame to cause tobacco to burn. The burning tobacco releases smoke containing nicotine that is inhaled by the smoker to deliver the nicotine to the lungs. In contrast, e-cigarettes heat a liquid, referred to as “e-liquid,” containing nicotine, and in some instances flavoring, to convert the liquid into a vapor that is inhaled by the smoker to deliver the nicotine to the lungs. E-cigarettes generally include a battery, an atomizer and a hollow, re-fillable cartridge that contains the liquid nicotine. Due to the frequency required to re-fill the cartridge, an advanced type of e-cigarette has been developed that combines the atomizer and the cartridge into a single “cartomizer” connected to the battery. Cartomizers allow for a greater length of time between e-liquid re-fills. The vaporization process is initiated by the smoker inhaling on the cartridge or cartomizer, or alternatively, by the smoker depressing a manual switch that activates the atomizer or cartomizer. The atomizer heats the e-liquid and converts the liquid into a nicotine vapor in the form of an aerosol. The nicotine vapor is inhaled through a mouthpiece provided on the tip of the cartridge or cartomizer to deliver the nicotine to the lungs of the smoker. The smoker then exhales the residual vapor in the form of cigarette smoke without any combustion by-products.
Despite the reduced health risks, there remain certain disadvantages with the current e-cigarettes. In particular, the e-liquid contained within the cartridge or cartomizer typically contain a solution of propylene glycol, vegetable glycerin (VG), and/or polyethylene glycol 400 (PEG400) mixed with concentrated flavors and a highly variable concentration of nicotine. However, the liquid solutions of certain e-cigarettes still have been found to contain known cancer-causing agents, referred to as tobacco-specific nitrosamines (TSNAs), as well as tobacco-specific impurities, such as anabasine, myosmine, and β-nicotine. In fact, in a recent study the Food and Drug Administration (FDA) detected diethylene glycol, a poisonous and hygroscopic liquid commonly used in anti-freeze solutions, in the e-liquid of one brand of e-cigarette, and measurable levels of nicotine in e-liquid cartridges that claimed to be nicotine-free. These findings are particularly disturbing since the cartridges and cartomizers of e-cigarettes are inherently susceptible to leakage and/or breakage owing to their small size and relative fragility. As a result, the danger exists that a cartridge or cartomizer could leak or break and cause a user to directly inhale a harmful dosage of the liquid solution or a full nicotine delivery without vaporization. It is also possible for a leaking e-liquid to damage the electronics and/or corrode the battery of the electronic nicotine delivery device. Furthermore, the majority of e-cigarettes utilize a rechargeable lithium battery that can potentially explode if the smoking device is mistakenly exposed to the flame from a match, lighter, torch or the like.
Accordingly, an improved device that is both effective, convenient and easy to use is needed for vaporizing and delivering an aerosol agent, for example a therapeutic drug in the form of an aerosol to a patient, or nicotine in the form of an aerosol to a smoker. Such a device must be capable of vaporizing and delivering a wide range of aerosol agents in a portable, reliable, repeatable and easy to use manner. As used herein, the term “aerosol” is intended to include vapors, gases, fine particles, and the like, both visible and invisible, generated by a heat source acting upon a means for forming an aerosol in a manner consistent with the present invention. As so defined, the term “aerosol” specifically includes any pharmacologically or physiologically active agents, and any desired additives, such as an aerosol forming agent, irrespective of whether they produce a visible aerosol. As used herein, the term “in heat conducting relation” is intended to mean a physical arrangement of two or more components whereby heat is transferred by conduction or convection from a heat generating source (e.g., a heating element) to a thermally conductive component (e.g., a heat conductor or a substrate) substantially throughout the heat generating period of the heat source. A heat conducting relation can be achieved by locating the components in fluid communication, direct physical contact or in close proximity to one another during operation of the heat source.